In the Birkat Hamazon on Yom Tov, we insert the “Ya’aleh Ve’Yavo” text before the blessing of “Boneh Yerushalayim,” as is printed in all Siddurim. One is obligated to eat bread during all Yom Tov meals; both during the night and day meals. Thus, if one mistakenly omitted the “Ya’aleh Ve’Yavo” text from Birkat Hamazon, if he remembers after he said the words “Baruch Ata Hashem” but before he said “Boneh Yerushalayim,” he should end off by saying “Lamedeni Chukecha” and then proceed to insert “Ya’aleh Ve’Yavo” (meaning that when has already said “Baruch Ata Hashem” he should not end off the blessing by saying “Boneh Yerushalayim,” rather he should say “Lamedeni Chukecha” and then proceed to recite “Ya’aleh Ve’Yavo”). If one only remembers that he omitted “Ya’aleh Ve’Yavo” after concluding the blessing of “Boneh Yerushalayim,” he should recite the following blessing there: “Baruch Ata Hashem Elokeinu Melech Ha’Olam Asher Natan Yamim Tovim Le’Yisrael Le’Sasson Ul’Simcha, Et Chag HaShavuot Hazeh Et Yom Tov Mikra Kodesh Hazeh, Baruch Ata Hashem Mekadesh Yisrael Ve’Hazemanin.”
If one has already started the fourth blessing of Birkat Hamazon (the blessing of “La’ad Hakel Avinu Malkeinu”), i.e. he concluded the blessing of “Boneh Yerushalayim” and has already begun to say “Baruch Ata Hashem Elokeinu Melech Ha’Olam” at which point he immediately remembers that he has forgotten to say “Ya’aleh Ve’Yavo,” he should continue with the text of “Asher Natan” (see above), and following that he should begin the fourth blessing anew.
If one remembers that he has omitted “Ya’aleh Ve’Yavo” only after reciting the words “La’ad Hakel Avinu Malkeinu,” he no longer goes back to recite it. Although the obligation to repeat Birkat Hamazon if one has forgotten “Ya’aleh Ve’Yavo” depends on whether or not eating bread is compulsory (for this reason, if one forgets to recite “Ya’aleh Ve’Yavo in Birkat Hamazon of Rosh Chodesh, he would not repeat Birkat Hamazon, for there is no obligation to eat bread on Rosh Chodesh) and as we have mentioned, there is an obligation to eat bread on the holiday of Shavuot which would seem to imply that one who forgets “Ya’aleh Ve’Yavo” must in fact repeat Birkat Hamazon, nevertheless, Maran Harav Ovadia Yosef Shlit”a writes that since the issue of the obligation to eat bread on Shavuot is subject to disagreement, as some Rishonim hold that if one does not wish to eat bread on Shavuot, he need not, for the only explicit Torah commandment to eat bread is on the first night of Pesach and the first night of Sukkot, but on Shavuot there is no such obligation; thus, although we follow the ruling of the Rambam and Rosh that there is indeed an obligation to eat bread on Shavuot as well, nevertheless, regarding the repetition of Birkat Hamazon, we follow the general rule of “when in doubt, do not bless,” meaning that due to the severity of the prohibition of uttering a blessing in vain, as long as a disagreement exists whether or not one must recite the blessing again, one does not repeat the blessing.
Although, in general, regarding Birkat Hamazon we do not follow the rule of “when in doubt, do not bless” as Birkat Hamazon is a Torah obligation and regarding such things, we have another general rule of “regarding a doubt pertaining to a Torah law, one must be stringent,” nevertheless, since mentioning “Ya’aleh Ve’Yavo” in Birkat Hamazon is only a Rabbinic enactment, if a dispute exists whether or not one must repeat Birkat Hamazon due to the omission of “Ya’aleh Ve’Yavo,” we indeed follow the original rule of “when in doubt, do not bless.”
